In recent years, a laser beam is used in various applications, for example, it is used to cut or machine metals, used as a light source of a photolithography device in a semiconductor manufacturing apparatus, used in various measuring instruments, or used in operations and treatment devices for surgery, opthalmology, dental surgery and the like.
When a solid-state laser (cited as a concept including semiconductor laser (or diode laser) in the present description) is used as such a laser light source, the wavelength of a laser beam emitted from the solid-state laser is in a region between the visible light region and the infrared region, and the method of directly generating ultraviolet light has not been established yet. The wavelength is too long to be used in, for example, an inspection apparatus. Because of this, the method of using light having a long wavelength emitted from such a solid-state laser by converting it into a deep ultraviolet light having a short wavelength (for example, the eighth harmonic wavelength of which is 193 nm) using a nonlinear optical crystal has been developed and disclosed in, for example, JP2001-353176 (patent document 1). As a nonlinear optical crystal used for such a purpose, BBO crystal, LBO crystal, CLBO crystal, and the like are known.
In such a laser light source, it is general that, for example, a laser beam generated from DFB-LD is amplified using a plurality of optical fiber amplifiers (FDFA) and then it is converted into deep ultraviolet light through the wavelength conversion optical system as described above. The optical fiber amplifier may include only one stage. However, in most cases the gain is increased by connecting a plurality of stages in series.
Such an optical fiber amplifier is configured by optical fibers as long as several meters and optical fiber components (optical component for an optical fiber amplifier). Because the optical fiber is long and the number of optical fiber components is large, when containing these fibers in a fixture, the optical fibers will get tangled in a complex manner and its task will be very complicated. In addition, in case an anomaly occurs in an optical fiber or an optical fiber component, it is difficult to locate the anomalous region, and therefore, the component cannot be replaced with another at once.
Further, in a state where the optical fibers are just wound and fixed, the state of the optical fibers may change due to vibrations during transportation.
On the other hand, in order to raise the output of an optical fiber amplifier, it is necessary to increase the pump power. However, accompanying an increase in pump power, heat is generated from the EDFA fiber. This diffused heat will cause an increase in an ambient temperature or a substrate temperature and affects adversely the optical fiber amplifier.
Consequently, if the optical fibers are contained in a state where the optical fibers get tangled in a complex manner and heat is generated from the EDFA fiber, the optical fiber amplifier is put in a very unstable state and it becomes difficult to stably oscillate a laser beam.
The present invention has been developed with such circumstances being taken into consideration and an object thereof is to provide a cassette for an optical fiber amplifier capable of containing an optical fiber amplifier orderly, an optical fiber amplifier using the same, and a light source device using the optical fiber amplifier.